The use of vortex forces is known in various arts, including the separation of matter from liquid and gas effluent flow streams, the removal of contaminated air from a region and the propulsion of objects. However, toroidal vortex flow has not previously been provided in a bagless vacuum device having light weight and high efficiency.
The prior art is strikingly devoid of references dealing with toroidal vortices in a vacuum cleaner application. However, an Australian reference has some similarities. This Australian reference does not approach the scope of the present invention, it is worth disusing its key features of operation so that one skilled in the art can readily see how its shortcomings are overcome by that which is disclosed herein.
In discussing Day International Publication number WO 00/19881 (the “Day publication”), an explanation of the Coanda effect is required. This is the ability for a jet of air to follow around a curved surface. It is usually referred to without explanation, but is generally understood provided that one makes use of “momentum” theory: a system based on Newton's laws of motion. Utilizing the “momentum” theory instead of Bernoulli's principles provides a simpler understanding of the Coanda effect.
FIG. 1 shows the establishment of the Coanda effect. In (A) air is blown out horizontally from a nozzle 100 with constant speed V. The nozzle 100 is placed adjacent to a curved surface 102. Where the air jet 101 touches the curved surface 102 at point 103, the air between the jet 101 and the surface 102 as it curves away is pulled into the moving airstream both by air friction and the reduced air pressure in the jet stream, which can be derived using Bernoulli's principles. As the air is carried away, the pressure at point 103 drops. There is now a pressure differential across the jet stream so the stream is forced to bend down, as in (B). The contact point 103 has moved to the right 104. As air is continuously being pulled away at point 104, the jet continues to be pulled down toward the curved surface 102. The process continues as in (C) with the contact point 105 moving farther to the right, until the air jet velocity V is reduced by air and surface friction.
FIG. 2 shows the steady state Coanda effect dynamics. Air is ejected horizontally from a nozzle 200 with speed represented by vector 201 tangentially to a curved surface 203. The air follows the surface 203 with a mean radius 204. Air, having mass, tries to move in a straight line in conformance with the law of conservation of momentum. However, it is deflected around by a pressure difference across the flow 202. The pressure on the outside is atmospheric, and that on the inside of the airstream at the curved surface is atmospheric minus ρV2/R where ρ is the density of the air.
The vacuum cleaner Coanda application of the Day publication has an annular jet 300 with a spherical surface 301, as shown in FIG. 3. The air may be ejected sideways radially, or may have a spin to it as shown with both radial and tangential components of velocity. Such an arrangement has many applications and is the basis for various “flying saucer” designs.
The simplest Coanda nozzle 402 described in the Day publication is shown in FIG. 4. Generally, the nozzle 402 comprises a forward housing 407, rear housing 408 and central divider 403. Air is delivered by a fan to an air delivery duct 400 and led through the input nozzle 401 to output nozzle 410. At this point the airflow cross section is reduced so that air flowing through the nozzle 402 does so at high speed. The air may also have a rotational component, as there is no provision for straightening the airflow after it leaves the air pumping fan. The central divider 403 swells out in the terminating region of the output nozzle 402 and has a smoothly curved surface 404 for the air to flow around into the air return duct using the Coanda effect.
Air in the space below the Coanda surface moves at high speed and is at a lower than ambient pressure. Thus dust in the region is swept up 405 into the airflow 409 and carried into the air return duct 406. For dust to be carried up this duct, the pressure must be low and a steady flow rate must be maintained. After passing through a dust collection system the air is sent through a fan back to the air delivery duct. Constriction of the airflow by the output nozzle leads to a pressure above ambient in this duct ahead of the jet. In sum, air pressure within the system is above ambient in the air delivery duct and below ambient in the air return duct.
Coanda attraction to a curved surface is not perfect. As shown in FIG. 5, not all the air issuing from the output nozzle is turned around to enter the air return duct. An outer layer of air proceeds in a straight fashion 501. When the nozzle is close to the floor, this stray air will be deflected to move horizontally parallel to the floor and should be picked up by the air return duct if the pressure there is sufficiently low. In this case, the system may be considered sealed; no air enters or leaves, and all the air leaving the output nozzle is returned.
When the nozzle is high above the ground, however, there is nothing to turn stray air that proceeded in a straight fashion 501 around into the air return duct and it proceeds out of the nozzle area. Outside air 502, with a low energy level is sucked into the air return to make up the loss. The system is no longer sealed. An example of what happens then is that dust underneath and ahead of the nozzle is blown away. In a bagless system such as this, where fine dust is not completely spun out of the airflow but recirculates around the coanda nozzle, some of this dust will be returned to the surrounding air.
Air leakage is exacerbated by rotation in the air delivery duct caused by the pumping fan. Air leaving the output nozzle rotates so that centrifugal force spreads out the airflow into a cone. The effect is to generate a higher quantity of stray air. Air rotation can be eliminated by adding flow straightening vanes to the air delivery duct, but these are neither mentioned nor illustrated in the Day publication.
A side and bottom view of an annular nozzle 600 is shown in FIG. 6. This is a symmetrical version of the nozzle shown in FIG. 4. Generally, the nozzle 600 comprises outer housing 602, air delivery duct 601, air return duct 605, flow spreader 603 and annular curved surface 604. Air passes down though the central air delivery duct 601, and is guided out sideways by flow spreader 603 to flow over an annular curved surface 604 creating the Coanda effect and is collected through the air return duct 605 by the tubular outer housing 602.
This arrangement suffers from the previously described shortcomings in that air strays away from the Coanda flow, particularly when the jet is spaced away from a surface.
While it is conceivable that the performance of the invention of the Day publication would be improved by blowing air in the reverse direction, down the outer air return duct and back up through the central air delivery duct, stray air would then accumulate in the central area rather than be ejected out radially. Unfortunately, the spinning air from the air pump fan would cause the air from the nozzle to be thrown out radially due to centrifugal force (centripetal acceleration) and the system would not work. This effect could be overcome by the addition of flow straightening vanes following the fan. However, none are shown, and one may conclude that the effects of spiraling airflow were not understood by the designer.
The Day publication has more complex systems with jets to accelerate airflow to pull it around the Coanda surface, and additional jets to blow air down to stir up dust and others to optimize airflow within the system. However, these additions are not pertinent to the analysis herein.
The problems with the invention of the Day publication are remedied by the Applicant's toroidal vortex vacuum cleaner. The toroidal vortex vacuum cleaner is a bagless design and one in which airflow must be contained within itself at all times. The contained airflow continually circulates from the vacuum cleaner nozzle, to a centrifugal separator, and back to the nozzle. Since dust is not always fully separated, some dust will remain in the airstream heading back towards the nozzle. The air already within the system, however, does not leave the system preventing dust from escaping back into the atmosphere. It is not sufficient to design the cleaner to ensure essentially sealed operation while operating adjacent to a surface being cleaned, operation must also remain sealed when away from a surface to prevent fine dust particles from re-entering the surrounding air.
Another reason for maintaining sealed operation when the apparatus is away from the surface is to prevent the vacuum cleaner nozzle from blowing surface dust around.
The Day publication, in most of its configurations, is coaxial in that air is blown out from a central duct and is returned into a coaxial return duct. The toroidal vortex attractor is coaxial, but operates the in the opposite direction. With the toroidal vortex attractor, air is blown out of an annular duct and returned into a central duct.
The inventor has also noted the presence of “cyclone” bagless vacuum cleaners in the prior art. The present invention utilizes an entirely different type of flow geometry allowing for much greater efficiency and lighter weight. Nonetheless, the following represent references that the inventor believes to be representative of the art in the field of bagless cyclone vacuum cleaners. One skilled in the art will plainly see that these do not approach the scope of the present invention, but they have been included for the sake of completeness.
Also relevant to the present invention are Dyson U.S. Pat. No. 4,593,429, Kasper et al. U.S. Pat. No. 5,030,257, Moredock U.S. Pat. No. 5,766,315, Tuvin et al. U.S. Pat. No. 6,168,641, and Song, et al. U.S. Pat. No. 6,195,835. However none of these references claim an invention as simple or efficient as the present invention.
Dyson U.S. Pat. No. 4,593,429 discloses a vacuum cleaning appliance utilizing series connected cyclones. The appliance utilizes a high-efficiency cyclone in series with a low-efficiency cyclone. This is done in order to effectively collect both large and small particles. In conventional cyclone vacuum cleaners, large particles are carried by a high-efficiency cyclone, thereby reducing efficiency and increasing noise. Therefore, Dyson teaches incorporating a low-efficiency cyclone to handle the large particles. Small particles continue to be handled by the high-efficiency cyclone. While Dyson does utilize a bagless configuration, the type of flow geometry is entirely different. Furthermore, the energy required to sustain this flow is much greater than that of the present invention.
Song, et al U.S. Pat. No. 6,195,835 is directed to a vacuum cleaner having a cyclone dust collecting device for separating and collecting dust and dirt of a comparatively large particle size. The dust and dirt is sucked into the cleaner by centrifugal force. The cyclone dust collecting device is biaxially placed against the extension pipe of the cleaner and includes a cyclone body having two tubes connected to the extension pipe and a dirt collecting tub connected to the cyclone body.
Specifically, the dirt collecting tub is removable. The cyclone body has an air inlet and an air outlet. The dirt-containing air sucked via the suction opening enters via the air inlet in a slanting direction against the cyclone body, thereby producing a whirlpool air current inside of the cyclone body. The dirt contained in the air is separated from the air by centrifugal force and is collected at the dirt collecting tub. A dirt separating grill having a plurality of holes is formed at the air outlet of the cyclone body to prevent the dust from flowing backward via the air outlet together with the air. Thus, the dirt sucked in by the device is primarily collected by the cyclone dust connecting device, thus extending the period of time before replacing the paper filter.
The device of Song et al. differs primarily from the present invention in that it requires a filter. The present invention utilizes such an efficient flow geometry that the need for a filter is eliminated. Furthermore, the conventional cyclone flow of Song et al is traditionally less energy efficient and noisier than the present invention.
Kasper et al. make use of a vortex contained in a vertically aligned cylinder comprising multiple slots running the length of the side of the cylinder. A vortex fluid flow is generated within the cylinder, thereby ejecting air, dirt, and other unwanted debris outward through the slots. The ejected air and debris then come into contact with the surface of a liquid. The liquid then captures the debris and the cleaned air is free to return to the inside of the cylinder. Cleaned air is further sent upwardly out of the cylinder.
The first major problem with Kasper et al. evolves from the use of a water bath. A liquid bath adds both weight and complexity. Additional maintenance is also required to change the liquid, prevent corrosion, etc. In contrast, the present invention does not utilize liquid to separate debris from air. In fact, the present invention can separate matter from liquids as well. Kasper et al.'s device could not achieve such results given that the liquid-air surface is integral for collecting particles. More specific to the cyclone separator, the cyclone is maintained solely by the wall of the cylinder. The present invention uses a solid surface to maintain cylindrical flow in conjunction with high pressure from the dust collector. No such pressure is provided in Kasper et al.'s patent; air is free to be ejected out the slots and return into the cylinder from beneath. Additionally, Kasper et al. mix circulating air ejected from the cyclone with non-circulating incoming air, thereby inducing energy losses. The present invention avoids this problem by ensuring that all incoming air is traveling in a circular path. Hence, the present invention is simpler, lighter, more efficient, and less noisy.
Tuvin et al. also make use of a cyclone separation system. The Tuvin et al. patent includes a cyclone separator that ejects particles outward from a cyclone. However, there are several major differences between the present invention and Tuvin et al. First, the means for creating the cyclone flow is not the same. The present invention utilizes an impeller, centrifugal pump, or propeller to create the cylindrical airflow necessary to achieve separation. In contrast, Tuvin et al.'s patent directs the air entering the cyclone chamber tangentially with the chamber's wall. Therefore, in Tuvin et al., the chamber's wall is what then forces the air into cylindrical flow.
In terms of efficiency, the present invention utilizes an impeller, propeller, or centrifugal pump to create the cylindrical flow and the necessary suction in a single step. This is advantageous from energy saving and simplicity standpoints since two separate steps are not necessary. In contrast, Tuvin et al. makes use of a filter as the final step before air exits the device. This is disadvantageous because filters impede airflow, consuming energy and compromising efficiency. Filters are not needed in the present invention because separation is sufficiently performed. Moreover, the present invention can remove both large and small particles in one step. Tuvin, et al.'s invention necessitates two steps, involving a coarse separator and a cyclone chamber. Therefore, the cyclone chamber must only be capable of separating fine particles. Efficiency is further reduced by these extra steps while complexity is added. Consequently, the present invention in simpler and more efficient then that disclosed in Tuvin et al.
Finally, Moredock U.S. Pat. No. 5,766,315 discloses a centrifugal separator that ejects particles radially. Nevertheless, the apparatus is not as simple and efficient as the present invention. In Moredock, the cylindrical flow is created by allowing air to enter the dome tangentially with respect to the wall. The same disadvantages concerning efficiency and simplicity apply. Also, the ejection duct used by Moredock differs significantly from the present invention's dust collector. Moredock ejects particles from the dome via a slot running vertically along the wall. The slot leads into a duct traveling away from the apparatus. The duct allows air to exit along with the particles. No indication of back-pressure is disclosed as in the present invention. Consequently, air pressure can not be used to maintain cylindrical flow. Without pressure assisting stabilization, airflow is further disrupted reducing the acceptable width of the slot. Furthermore, Moredock allows air to exit the system. This air is still dust-laden and needs further cleaning. Also in Moredock, kinetic energy from the exiting air is lost from the system. However, the present invention keeps the dust-laden air within the chamber and dust collector. No dust-laden air is allowed to exit. Therefore, the present invention is not only simpler, more efficient, but also more effective than that disclosed in Moredock.
Thus, there is a clear and long felt need in the art for a light weight, efficient and quiet bagless vacuum cleaner which prevents dust laden air from flowing into the atmosphere.